Many of the beneficial metabolic effects of endurance exercise training are not due to adaptations to weeks, months, or even years of training, but rather much is due to the response to the most recent exercise session(s). Therefore, the investigators contend that lifestyle interventions for obese individuals should be tailored to optimize the metabolic effects of the most recent exercise session(s). But the "dose" of exercise necessary to evoke these beneficial responses is not known, and the mechanisms responsible for these improvements are poorly understood. The findings from these studies will: 1) establish the minimum "dose" of a single exercise session necessary to improve insulin sensitivity the next day in obese adults, 2) characterize the underlying metabolic factors responsible for the improvement in insulin sensitivity, and 3) assess the cumulative metabolic adaptations that occur over days, weeks, and months of a low-intensity/low-volume lifestyle exercise program. Findings from these studies will provide valuable information for the development of lifestyle programs aimed at maximizing the key metabolic health benefits of each exercise session in obese patients.

Inclusion Criteria:

• Body Mass Index [BMI] = 30-45 kg/m2, weight stable (± 5 lbs in the past month), fasting blood glucose concentration must be <125 mg/dl.

Exclusion Criteria:

• pregnancy, evidence of cardiovascular or metabolic disease, taking medications know to influence metabolism.